Path planner and method for planning a contour path of a vehicle

ABSTRACT

In accordance with one embodiment of the invention, a path planer and method for planning a path of a vehicle defines a reference row having a reference contour in a work area. A representation of the defined reference row is established. The defined reference row comprises a curved component, a generally linear component, or both. A generator generates one or more contour rows with a tracking contour that tracks or mirrors the reference contour based on a vehicular width and a radius difference parameter associated with the curved component. The contour rows are generated by a translation technique for the generally linear component and a radius modification technique for the curved component.

This is a continuation-in-part of Ser. No. 10/403,681, filed Mar. 31,2003, and entitled “A PATH PLANNER AND METHOD FOR PLANNING A PATH OF AWORK VEHICLE” (Attorney Ref. No. 16435-US).

FIELD OF THE INVENTION

This invention relates to a path planner and method for planning acontour path of a vehicle.

BACKGROUND OF THE INVENTION

A path planner may be used to determine one or more path plans for avehicle to cover a work area. The work area may represent a field forgrowing a crop or other vegetation. The vehicle may need to traverse theentire work area or a portion thereof to plant a crop (or precursorthereto), treat a crop (or precursor thereto), or harvest a crop, forexample. If the path plan is limited to linear rows, the execution ofthe path plan may consume more energy than desired to traverse slopedterrain or a work area of a particular shape. Accordingly, there is aneed for a system and a method for applying contour path plan for thevehicle to the work area.

SUMMARY OF THE INVENTION

In accordance with one embodiment of the invention, a path planner andmethod for planning a path of a vehicle defined a reference row having areference contour in a work area. A representation of the definedreference row is established. The defined reference row comprises acurved component, a generally linear component, or both. A generatorgenerates one or more contour rows with a tracking contour that tracksor mirrors the reference contour based on a vehicular width and a radiusdifference parameter associated with the curved component. The contourrows are generated by a translation technique for the generally linearcomponent and a radius modification technique for the curved component.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a path planner for planning a path of avehicle, where the path planner is incorporated into a vehicleelectronics.

FIG. 2 is a block diagram of an illustrative path planner in greaterdetail than FIG. 1.

FIG. 3A is a flow chart of one embodiment of a method for generatingcontour rows or a path plan to cover a region.

FIG. 3B is a flow chart that illustrates step S104 of FIG. 3A in greaterdetail.

FIG. 3C is a flow chart of another embodiment of a method for generatingcontour rows or a path plan to cover a region.

FIG. 4 is a flow chart of a first procedure for generating contour rowsto resolve interference within a contour row of a contour path plan.

FIG. 5 is a flow chart of a second procedure for generating contour rowsto resolve interference within a contour row of a contour path plan.

FIG. 6 is a flow chart of a method for generating contour rows pursuantto a search algorithm for searching candidate radius differenceparameters to identify a preferential radius difference parameter.

FIG. 7 is a top view of a first illustrative path plan where a referencerow is aligned with a bottom border or boundary of the work area andwhere the turns at the end of the rows are omitted solely to simplifythe drawing.

FIG. 8 is top view of a second illustrative path plan where a referencerow is aligned with a top border or boundary of the work area and wherethe turns at the end of the rows are omitted solely to simplify thedrawing.

FIG. 9 is a top view of third illustrative path plan where a referencerow is aligned with a left and top border or boundary of the work areaand where the turns at the end of the rows are omitted solely tosimplify the drawing.

FIG. 10 is top view of a fourth illustrative path plan where a referencerow is aligned with a right wavy diagonal border of the wok area andwhere the turns at the end of the rows are omitted solely to simplifythe drawing.

FIG. 11 and FIG. 12 are top views of a fifth illustrative path plan anda sixth illustrative path plan, respectively, where a reference contourof a reference row is unrelated to a border contour of the work area.

FIG. 13 is a diagram of an illustrative contour reference row inaccordance with the invention.

FIG. 14 is a diagram of a path plan derived from the illustrativecontour reference row of FIG. 13.

FIG. 15A is a first representation of a contour row in accordance withgenerally linear segments and arc segments.

FIG. 15B is a second representation of a contour row defined by one ormore corners.

FIG. 15C is a third representation of a contour row defined by atransition sequence.

FIG. 16 is an example of generation of a next contour row associatedwith an arc of a previous contour row.

FIG. 17 is an example of a contour translation associated with thegeneration of a next contour row associated with an arc of a previouscontour row, where nesting contour applies.

FIG. 18 is an example of nesting contour associated with the generationof multiple next contour rows associated with an arc of a previouscontour row.

FIG. 19 is an illustrative example of the resolution of potentialinterference associated with two proximate outside corners.

FIG. 20 is an illustrative example of the identification of an outsidecorner-inside corner interference.

FIG. 21A illustrates a work area containing one or more obstacles orno-entry areas and having a defined reference contour row.

FIG. 21B illustrates the defining of transparency of contours that trackthe reference contour row on a first side of the reference contour rowand a second side of the reference contour row.

FIG. 21C illustrates a coverage solution that uses contour components tocover the work area of FIG. 21A.

FIG. 22 is a block diagram of an alternate embodiment of a path plannerfor planning a path of a vehicle.

FIG. 23 is a flow chart of a method for determining whether to use alinear path plan or a contour path plan, consistent with the pathplanner of FIG. 22.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In accordance with one embodiment of the invention, FIG. 1 illustrates apath planning system 11 which includes a path planner 10. The pathplanner 10 is coupled to a vehicle controller 16 and alocation-determining receiver 19. In turn, the vehicle controller 16 iscoupled to at least one of a steering system 20, a braking system 22 (ifpresent), and a propulsion system 24 of a vehicle. The vehiclecontroller 16 is associated with a safeguarding system 18 that mayinterrupt or over-ride the path plan or path planner 10 during executionof the path plan or movement of the vehicle for safety reasons, orotherwise.

The path planner 10 of FIG. 1 comprises a perimeter training module 14and a contour region-filling module 12. The perimeter training module 14is arranged to collect location data on one or more points along theperimeter of the work area or a defined region within the work area. Forexample, the perimeter training module 14 may collect location data(e.g., Global Positioning System coordinates) from thelocation-determining receiver 19 (e.g., GPS receiver with differentialcorrection). The location data is made available to contourregion-filling module 12 or to the reference row definer 26 (FIG. 2).

The contour region-filling module 12 establishes a path plan comprisingone or more contour rows to cover the work area or a region thereof.Although generally linear rows may be employed as part of a path plan,the path plan may be structured to support back-and-forth contour sweepsto cover a region of the work area. For certain regions of a work area,contour path plans may be more energy efficient and reduce fuelconsumption over linear rows. Whether or not contour rows are moreefficient than linear rows may depend upon the following: any decreasein the number of end-row turns for contour rows versus linear rows for agiven proposed path plan; and any increase in the length of contour rowsversus linear rows for the given proposed path plan. The decision ofwhether to use generally linear path plan, a contour path plan, or acombination of the linear path plan and the contour path plan isdiscussed in greater detail in conjunction with the embodiment of FIG.22 and FIG. 23.

Returning to consider FIG. 1, the vehicle controller 16 accepts an inputof the path plan and controls the vehicle consistent with the path plan,unless the safeguarding system 18 detects an obstacle, obstruction,hazard, safety condition, or other event that requires the vehicle todepart from the planned path, to stop movement or take evasive measuresto avoid a collision with an object or living being (e.g., person oranimal). The vehicle controller 16 may generate control signals for thesteering system 20, a braking system 22 (if present), and a propulsionsystem 24 that are consistent with tracking the path plan. For example,the control signals may comprise a steering control signal or datamessage that is time dependent and defines a steering angle of thesteering shaft; a braking control signal or data message that definesthe amount of deceleration, hydraulic pressure, or braking frictionapplied to brakes; a propulsion control signal or data message thatcontrols a throttle setting, a fuel flow, a fuel injection system,vehicular speed or vehicular acceleration. If the vehicle is propelledby an electric drive or motor, the propulsion control signal or datamessage may control electrical energy, electrical current, or electricalvoltage to the electric drive or motor.

The steering system 20 may comprise an electrically controlled hydraulicsteering system, an electrically driven rack-and-pinion steering, anAckerman steering system, or another steering system. The braking system22 may comprise an electrically controlled hydraulic braking system, oranother electrically controlled friction braking system. The propulsionsystem 24 may comprise an internal combustion engine, an internalcombustion engine—electric hybrid system, an electric drive system, orthe like.

The vehicle has a vehicular width that may be defined as the greater ofthe width of the vehicular body or chassis or the outermost widthbetween the outer surface (e.g., side walls) of the wheels or tires onopposite sides of the vehicle. For certain vehicles, the vehicular widthmay vary from the implement width, swath width, cutting width, plowingwidth, planting width, harvesting width, seeding width, or another taskwidth associated with performing a task (e.g., an agronomic task,construction task, or lawn and garden task). For instance, the taskwidth (e.g., mowing width) of a mower may depend upon the length of therotary cutting blade or group of cutting blades. The rotary cuttingblade or blades may have an effective cutting width that is more or lessthan the vehicular width. The safeguarding system 18 may use the greaterof vehicular width and the task width (or both) to avoid collisions withobjects or obstacles, whereas the path planner 10 may use the task widthto establish an offset or desired overlap between adjacent paths withina work area in accordance with a path plan. The offset or desiredoverlap may depend upon whether a crop input or chemical is appliedversus whether a harvesting or mowing operation is executed, forinstance.

FIG. 2 is a block diagram of a path planner 10. The path planner 10comprises a contour region-filling module 12. The contour region-fillingmodule 12 includes a reference row definer 26, a representation former28, and a generator 30. The reference row definer 26 communicates withthe representation former 28. In turn, the representation former 28communicates with the generator 30.

The definer 26 defines the reference row having a reference contour. Thereference contour may be defined in accordance with various techniquesthat may be applied alternately and cumulatively. Under a firsttechnique, the reference contour follows along a boundary contour of aboundary of the work area. Under a second technique, the referencecontour follows along a boundary contour of the work area and thereference row is generally contiguous with the boundary. Under a thirdtechnique, the definer 26 may define a reference row that does not tracka boundary of the work area.

The representation former 28 defines the reference row in accordancewith one or more representations. Each representation may represent thegenerally linear components and generally curved components of thereference row. For example, the representation former 28 may define thearc segment as a center point, a start point, an end point and a radius,where the arc segment has a radius greater than the minimum turningradius of the vehicle. The representation former 28 may define thelinear segment as two points. The start point, end point, and otherpoints may be expressed as two dimensional or three dimensionalcoordinates.

The generator 30 comprises a coordinator 32, a translator 34 and aradius modifier 36 for determining a group of tracking contours thattrack the reference contour within a region of a work area. Thetranslator 34 may translate or apply a translation technique to agenerally linear component (e.g., a linear segment) of the referencerow, whereas the radius modifier 36 may use a radius modificationtechnique for the generally curved component (e.g., an arc segment) ofthe reference row to generate a group of tracking contours for the workarea. In one embodiment, the radius modifier 36 selects the radiusdifference parameter (e.g., p) such that if the radius differenceparameter generally equals the vehicular width (e.g., w) , a nestingcontour solution applies to adjacent contour rows of a path plan on alocal basis.

The generator 30 further comprises a search engine 38 for applying asearch algorithm to possible candidate values of the radius differenceparameter to identify a preferential radius difference parameter. In oneconfiguration, the search engine 38 limits the search space such thatthe radius difference parameter is bounded by a candidate radiusdifference parameter generally equal to or less than the vehicular widthto reduce data processing resources required for the path planner 10, toreduce power consumption and to provide a rapid solution for vehicularguidance in accordance with a path plan. For example, the search spacemay be limited such that search is started with the radius differenceparameter equal to the vehicular width and the radius differenceparameter is decreased therefrom to find a preferential value ofpotential nonconformity or rule violation by the radius differenceparameter.

In one embodiment, the interference module 40 identifies the presence ofpotential path plan formation rule violations or potentialnonconformities. For example, a nonconformity or path plan formationrule violation may occur where (1) two proximate outside arcs areadjacent or separated by a linear segment in previous (e.g., an outercontour row located toward an outer boundary of the work area) and (2) anext adjacent row (e.g., an inner contour row located toward an interiorof the work area) has insufficient space to fit two tracking arts thattrack the two outside arcs of the previous row. Accordingly, theinterference module 40 may resolve the potential path plan formationrule violation or potential nonconformity by determining a singleoutside arc for an inner contour row that tracks the outer contour row.The inner contour row and the outer contour row represent a portion of acontour path plan for a work area. The inner contour row is locatedcloser to an interior of the work area than the outer contour row. Anoutside or outer contour row refers to a contour row that is locatedmore toward the boundary of the work area than an inner contour row. Aninner arc is part of an inner contour row, whereas an outer arc is partof an outer contour row. An inside arc refers to an arc with its convexside facing an interior of the work area and an outside arc refers to anarc with its convex side facing outside of the work area. An adjacentarc refers to arcs without any intervening arc segments of material sizeor intervening linear segments of material length on the same contourrow.

In another embodiment, the interference module 40 identifies thepotential nonconformity of an inside arc and outside arc being adjacentto each other, in a contour row where such inside arc and outside arcwould cross over each other; and the interference module 40 applies aniterative repair process to reformulate the contour row. An inside arcrefers to an arc with its convex side facing an interior of the workarea and an outside arc refers to an arc with its convex side facingoutside of the work area. An iterative repair process refers to aprocess in which a set of rules are applied to provide a solution foradjacent contour rows that minimizes, but permits greater thanpreviously allotted overlap between two rows for a region of the workarea. The previously allotted overlap may be based on the task width orimplement width. Ideally, the previously allotted overlap betweenadjacent contours is barely sufficient to eliminate substantiallyunharvested, unmowed, or unprocessed regions of the work area, whereasthe greater overlap of the iterative repair process is authorized onlywithin a confined region (e.g., a group of contour rows along a portionof their length) about the identified potential nonconformity.

FIG. 3A is a method for planning a path of a vehicle. The method ofplanning a path of a vehicle begins in step S100.

In step S100, a path planner 10 or a definer 26 defines a reference rowhaving a reference contour in a work area. The path planner 10 ordefiner 26 may define the reference contour in accordance with variousalternative techniques. Under a first technique, the path planner 10 orthe definer 26 may define the reference row having a reference contourthat follows along a boundary contour of a boundary of the work area.For example, the definer 26 may define reference location dataassociated with one or more boundaries of the work area to support thefirst technique. Under a second technique, path planner 10 or thedefiner 26 may define the reference row having a reference contour thatfollows along a boundary contour of a boundary of the work area and thereference row is contiguous with the boundary. Under a third technique,the definer 26 comprises defining a reference row that does not track aboundary of the work area.

In one embodiment, a user defines or specifies a reference contour oranother initial travel row that the user wants the coverage rows tofollow. The initial shape of the reference contour serves as the patternfor consecutive travel rows one or more sides of the reference contour.Contours can be used to minimize the number of end-row turns for acoverage solution. Other uses for contour shapes are to minimize theerosion of sloped areas, to minimize vehicular energy consumption, or tominimize the time to complete a work task (e.g., harvesting of a fieldor applying crop inputs).

In one embodiment, the reference contour forms an open shape. An openshape is defined as a shape that does not contain a loop. An open shapeis also defined as a shape that does not contain a loop and does notclose in on itself if one extends the reflection of the start vector andthe final vector to infinity. The user interface 21 may return an errorto the user via the user interface 21 for a defective reference contouror a pathological reference contour defined by a user. For instance, adefective reference contour might to prevent the path planner 10 frombuilding contour travel rows where the neighboring arcs quickly interactin an undesired manner or violate other prohibited path formation rules.

In step S102, a representation former 28 establishes a representation ofthe defined reference row. The reference row comprises a generallycurved component, a generally linear component, or both, regardless ofthe type of representation.

In step S102, the representation of the reference row may be structuredin accordance with various representations, which may be appliedcumulatively or individually. Under a first representation, the pathsegment or contour row comprises a generally linear segment associatedwith one or more arc segments. For example, the generally linear segmentmay be connected end-to-end with one or more arc segments. The contourregion-filling module 12 or representation former 28 may define the arcsegment as a center point, a start point, an end point and a radius,where any arc segment has a radius greater than the minimum radius.Further, the contour region-filling module 12 or former 28 may definethe linear segment as two points. The start point, end point, and otherpoints may be expressed as two dimensional or three dimensionalcoordinates.

Under a second representation, the path segment or contour row comprisesa sequence of one or more corners. Each corner is defined with locationdata (e.g., coordinates) and a particular sequence for traversing thecorners or location data. Under a third representation, the path segmentor row contour comprises location data and a heading associated withcorners or points on the path segment.

The third representation is defined by pairs of location data associatedwith heading data. Each pair is assigned part of a sequence or order tofacilitate traversal of a particular contour path. Each pair may beassociated with a critical point on a particular contour path. Acritical point may be defined as a point where a material change indirection of the vehicle occurs or is planned.

In a fourth representation for carrying out step S102, the contourregion-filling module 12 or the representation former 28 defines therepresentation as a list or a series of location data for correspondingpoints on the reference contour. For example, the fourth representationmay represent a collection of points spaced approximately equidistantlyor with a desired resolution or granularity within the work area.

In step S104, a path planner 10 or generator 30 generates one or morecontour rows with a tracking contour that tracks or mirrors thereference contour based on a vehicular width and a radius differenceparameter associated with the arc segment. The contour rows aregenerated by a translation technique for the generally linear components(e.g., linear segments) and a radius modification technique for thecurved components (e.g., arc segments).

The first representation (previously described in step S102) of acontour row is well-suited for processing the linear segment inaccordance with a translation technique and the arc segment inaccordance with a radius modification technique to derive a group ofcontour rows that track each other. The second representation iswell-suited for processing the corners (and linear components) inaccordance with a translation technique, without the need for any radiusmodification, to develop the contour rows within the work area. Thethird representation or the fourth representation may be applied to atranslation technique, a radius modification technique, or both todevelop the contour rows.

The translation technique of step S104 may be carried out as follows:The vehicle minimum turning radius, the task width (w) and one contourrow (e.g., reference row) are inputted as input data into the pathplanner 10 as a sequence of generally linear components (e.g., linesegments) and curved components (e.g., arc segments). The path planner10 or translator 34 processes the input data to produce the next contourrow (or successive remaining contour rows to cover a work area) as asequence of generally linear components (e.g., linear segments), curvedcomponents (e.g., arc segments), or both. The next row, if produced, isselected to (a) minimize the local overlap with the input row (e.g.,adjacent row or immediately preceding row), unless necessary to resolvea potential nonconformity or plan formation violation; (b) not to leaveany gaps with the input row (e.g., adjacent row or immediately precedingrow); and (c) never create an arc or curved portion whose associatedradius is less than the minimum turning radius of the vehicle. The nextrow should be drivable by the vehicle given its constraints andgeometrically or physically possible to execute, as defined by rules orconditions (e.g., if-then statements).

The translation technique iterates to generate one or more next rowsuntil the new next row produced would be outside the work area. Theiterations are used to fill a first region of the work area that lies onat least one side of the original reference row. The first region isfilled with a first set of contour rows. If the second region or otherside of the reference row is not filled with contour rows, the abovetranslation technique is applied again as described above to provide asecond set of contour rows. The reference row, the first set of contourrows, the second set of contour rows and interconnected turns form acomplete contour coverage pattern.

In accordance with the radius modification technique, if the radiusdifference parameter generally equals the vehicular width, a translationor nesting solution applies to adjacent rows on a local basis. However,if the radius difference does not equal the vehicular width, atranslation or nesting solution does not apply to the adjacent rows andthe following radius modification technique is applied to the curvedcomponents of the reference row. The radius modification techniquecomprises using the process which is more fully described in conjunctionwith FIG. 16.

FIG. 38 is a procedure for carrying out step S104 of FIG. 3A. Theprocedure of FIG. 3B starts in step S320.

In step S320, a data processing system or path planner 10 determines ifthe reference row is contiguous with a side of a region (e.g., the workarea). If the reference row is continuous with a side of the region(e.g., work area), the procedure continues with step S322. However, ifthe reference row is not contiguous with a side of the region, theprocedure continues with step S324.

In step S322, the path planner 10 or generator 30 generates trackingcontours on an interior side of the reference row within the region.

In step S324, the path planner 10 or generator 30 generates trackingcontours on a first side of the reference row and a second side of thereference row to cover the entire region (e.g., work area), lessobstacles or keep-out zones.

The method of FIG. 3C is similar to the method of FIG. 3A, except FIG.3C further includes steps S314, S316, S318, and S320. Like referencenumbers in FIG. 3A and FIG. 3C indicate like procedures or techniques.

In step S314, the path planner 10 or generator 30 overlays the generatedcontour rows over a region associated with the work area. The region maybe located within the work area. In one illustrative example, theboundaries of the region may be coextensive with the boundaries of thework area.

In step S316, the path planner 10 or generator 30 truncates the contourrows at an intersection of the contour rows and a boundary of theregion.

In step S318, the path planner 10 or generator 30 determines apreferential order for the vehicle to traverse each row based onvehicular constraints (e.g., turning radius) and based on a search ofcandidate orders or candidate sequences. For example, the path planner10 may select the preferential order to reduce or minimize energyconsumption, fuel consumption, estimated total path distance, orestimate total path completion time.

In step S320, the path planner 10 or generator 30 interconnects thecontour rows in the preferential order with turns to form a generallycontinuous path plan of back and forth sweeps that cover the region.

FIG. 4 is a procedure for managing a potential nonconformity orprohibition of a path formation rule. Here, the potential noncomformitycomprises interference between two proximate (e.g. adjacent) outsidearcs. An inside arc refers to an arc with its convex side facing aninterior of the work area and an outside arc refers to an arc with itsconvex side facing outside of the work area. The method of FIG. 4resolves interference where the configuration of tracking contour rowsmight otherwise lead to inefficient and sometimes impossible pathsbecause of various interactions among the geometric constraints of theinitial contour row and the minimum turning radius of the vehicle. Themethod of FIG. 4 begins in step S106 and may be applied during or afterstep S104 of FIG. 3A.

In step S106, an interference module 40 identifies the presence of twoproximate outside arcs that are adjacent or separated by a linearsegment in an outer contour row located toward an outer boundary of thework area. The inner contour row and the outer contour row represent aportion of a contour path plan for a work area. The inner contour row islocated closer to an interior of the work area than the outer contourrow. An outside or outer contour row refers to a contour row that islocated more toward the boundary of the work area than an inner contourrow. An inner arc is part of an inner contour row, whereas an outer arcis part of an outer contour row. An adjacent arc refers to arcs withoutany intervening arc segments of material size or intervening linearsegments of material length (e.g., greater than a define thresholdlength) on the same contour row.

In step S108, the interference module 40 determines a single outside arcfor an inner contour row that tracks the outer contour row, the innercontour row located closer to an interior of the work area than theouter contour row. The signal outside arc replaces, in effect, thepotential use of two outside arcs (in the inner contour row) that trackthe outer contour row.

The above algorithm for producing the next contour row can beiteratively applied to compute the complete contour coverage path. Wheregeometric constraints between adjacent arcs cause interference or wherethe translation technique, and radius modification techniques do notresolve the interference, the method of FIG. 4 may be applied.

Referring to FIG. 4 in combination with FIG. 19, an outsidecurve-outside curve interference is addressed. This problem arises wheretwo adjacent outside curved components (e.g., arc segments or corners)converge together and there is no longer room to fit both curvedcomponents in the contour row. As illustrated in FIG. 19, thebisect-lines (e.g., first bisect line 914 and a second bisect line 918)of the corresponding curved components (e.g., first curved component 900and second curved component 902) intersect. The intersection pointassociated with the intersection of the bisect lines may be referred toas the bisect-line intersection point 902. The problem of interferencebetween two adjacent outside curved components is detected whenever thecenter-point (e.g., coincident a radius of the curved component or arcsegment) of a curved component (e.g., or estimated radius of a corner)crosses over inwardly and goes beyond inwardly with respect to thebisect-line-intersection point 912.

If the above outside-outside interaction is detected between aniteration of the translation of a contour or a procedure for determininga next contour row, the interference module 40 or path planner 10corrects or resolves the interference by replacing the two interactingcurved components (e.g., corners) with a single curved component 904(e.g., corner). This process is referred to as subsuming corners and isillustrated in FIG. 19. The new single curved component 904 (e.g.,corner) will lie along a new bisect-line 920 that intercepts thebisect-line intersection point 912. For example, the next contour maycomprise a corner with a vertex 910. The radius of the new corner isestimated to minimize the overlap to the previous row. The abovecorrective process of subsuming corners may occur multiple times,depending upon the complexity of the originating reference row.

FIG. 5 is a procedure for managing interference between an adjacentinside arc and outside arc. An inside arc refers to an arc with itsconvex side facing an interior of the work area and an outside arcrefers to an arc with its convex side facing outside of the work area.The method of FIG. 5 resolves interference where the configuration oftracking contour rows might otherwise lead to inefficient and sometimesimpossible paths because of various interactions among the geometricconstraints of the initial contour row and the minimum turning radius ofthe vehicle. The method of FIG. 5 may be applied simultaneously with orfollowing step S104 of FIG. 3A. The method of FIG. 5 begins in stepS110.

In step S110, the path planner 10 or interference module 40 identifiesthe presence of the following two conditions. Under a first condition,an inside arc and outside arc are adjacent to each other, or interwinedin a contour row. Under a second condition, an inside arc and outsidearc would cross over each other. If both of the foregoing conditions arepresent, the method continues with step S112. Otherwise, the process ofFIG. 5 ends in step S111.

In step S112, the interference module 40 applies an iterative repairprocess to reformulate the contour row. The iterative repair process mayamount to the relaxation or local suspension of a desired overlapbetween adjacent rows or a select region, while maintaining the desiredoverlap elsewhere in the work area. The path planner may change theparameters of the offending contour row (and even adjacent rows) andtries another solution iteratively on a trial-and-error basis or inaccordance with a search algorithm until suitable resolution isachieved.

Referring to FIG. 5 and FIG. 20, an interference between an insidecurved component and outside curved component is addressed for theestablishment of a new contour row based on a previous contour row orreference contour. The interference condition is illustrated in FIG. 20where an inside arc segment 991 and an outside arc segment 990 approacheach other in a first contour row 952 while the room to fit both arcs isbeing reduced each iteration or successive row (e.g., second contour row950) of the path plan. The interference problem, illustrated in FIG. 20,is detected prior to or when the path planner attempts to connect thetwo transition points associated with two corresponding curvedcomponents (e.g., arc segments) with a smooth path. Because the pathplanner does not wish to create arcs that loop over and cross each other(as indicated by the cross-hatched section labeled 993), the pathplanner is instructed or programmed to address the interference asdescribed in conjunction with FIG. 5.

FIG. 6 is a procedure for searching for a radius that may be applied inaccordance with the radius modification technique in step S104 of FIG.3. Step S114 may be executed simultaneous with or after step S104, forexample.

In step S114, a generator 30 or search engine 38 applies a searchalgorithm to possible candidate values of the radius differenceparameter, wherein the search space is limited such that the radiusdifference parameter is bounded by a candidate radius differenceparameter generally equal to or less than the vehicular width. Given aninitial reference row, there are many possible contour paths that couldbe produced from it. In the approach outlined here, a hybrid oftranslation and radius modification (e.g., where nesting paths are aspecial case of radius modification) are created. The radiusmodification is controlled by a radial spacing parameter (p), which isthe difference in the radius between corresponding arc segments.Ideally, the paths should be produced with the radial spacing parameter(p) set to the vehicular width (w), so that overlap between adjacentrows is minimized and a nesting contour solution applies. However, thesesolutions are often not possible due to the combined geometricconstraints of minimum-turning radius, and the interactions of adjacentarcs segments.

The algorithm uses a combination of generate-and-test and iterativerepair to find a complete solution that satisfies the geometricconstraints while minimizing the overlap. A search is made through thespace of possible values of p for each corner in the initial contourrow. If there are n initial corners and p is fixed as an integer, therewill be approximately O(w^(n)) possible combinations because p can varybetween 0 and the vehicular width (w). Where p is equal to zero, thepath planner instructs the vehicle to execute a totally redundant passof the vehicle over the same path or previous contour.

Rather than searching all possible combinations, an iterative greedymethod may be used for the sake or efficiency and reduction of dataprocessing resources. Each corner is individually optimized, by settingits p value to width and decreasing it until a valid solution is found.The largest value without failure is used in the final solution. Themethod proceeds by optimizing each corner individually until all thecorner p values have been set. The solution with the greatest p valuesis returned, since this will necessarily minimize the overlap andprovide an efficient contour path plan for the vehicle.

FIG. 7 through FIG. 12 illustrate various contour path plans in whichalternating rows or adjacent contour rows are shown as unshaded strips705 and shaded strips 707.

FIG. 7 is top view of a first illustrative path plan or contour pathplan including a contour row aligned with a bottom border 709 orboundary of the work area. Although turns between different or adjacentrows are not shown, it is understood that turns at the end of the rowsare omitted solely to simplify the FIG. 7. In one example, the contourpath plan of FIG. 7 tracks a reference row associated with or FIG. 7shows a contour path plan that tracks a reference row associated with orcoextensive with a lower boundary of the work area.

FIG. 8 is top view of a second illustrative path plan or contour pathplan including a contour row aligned with a top border 711 or boundaryof the work area. Although turns between different or adjacent rows arenot shown, it is understood that turns at the end of the rows areomitted solely to simplify the drawing. In one example, the contour pathplan of FIG. 8 tracks a reference row associated with or coextensivewith an upper boundary of the work area.

FIG. 9 is top view of a third illustrative path plan or contour pathplan where a contour row is aligned with a left border and top border715 or boundary of the work area. Although turns between different oradjacent rows are not shown, it is understood that turns at the end ofthe rows are omitted solely to simplify the drawing. In one example, thecontour path plan of FIG. 9 tracks a reference row associated with theleft and top border or boundary of the work area.

FIG. 10 is top view of a fourth illustrative path plan where a contourrow is aligned with a right wavy diagonal border 717 of the work areaand where the turns at the end of the rows are omitted solely tosimplify the drawing. In one example, the contour path plan of FIG. 10tracks a reference row associated with a wavy border or boundary of thework area.

FIG. 11 and FIG. 12 are top views of a fourth illustrative path plan anda fifth illustrative path plan, respectively, where a reference contourof a reference row or contour row is unrelated to a border contour(e.g., 719 or 721) of the work area. The path planning system and methodis flexible such that the path plans of FIG. 7 through FIG. 12, arepossible, among other path plans or contour path plans.

FIG. 13 is a diagram of an illustrative contour reference row 1301 inaccordance with the invention. In FIG. 13, a reference row represents acontiguous sequence of arc segments (A, B, C, and D) and generallylinear segments 1308 consistent with the first representation of thereference contour. Each arc segment may be defined by a radius, abeginning point, an end point, and a center point, for instance.

FIG. 14 is a diagram of a path plan derived from the illustrativecontour reference row 1301 of FIG. 13. The contour path plan computedfrom the reference row 1301 of FIG. 13 may use any of the embodimentsand procedures disclosed in this document. The turns at the end of rowsare omitted in FIG. 14 to simplify the illustration.

In FIG. 14, because the inside region or interior of the work area isabove the reference row, arcs A, B and D are referred to as outsidearcs, while arc C is an inside arc. An inside arc refers to an arc withits convex side facing an interior of the work area and an outside arcrefers to an arc with its convex side facing outside of the work area.

FIG. 15A and FIG. 15C represent alternative representations of referencecontours, contour rows, or tracking contours. Each reference contour maybe associated with a linear component, a curved component, or both,regardless of the applicable representation. The set of flexiblerepresentations for contour rows are illustrated in FIG. 15A throughFIG. 15C, inclusive. The representations include the following: (1) afirst representation comprising linear segments 500 and arc segments 502in FIG. 15A (2) a second representation comprising corners, and (3) athird representation comprising a transition sequence. The firstrepresentation, the second representation and the third representationssupport a translation technique (and nesting operations).

FIG. 15A is a first representation of a contour row in accordance withlinear segments 500 and arc segments 502. The linear segments 500 andarc segments 502 are oriented end for end. Each linear segment 500 maybe defined by the coordinates (e.g., two dimensional or threedimensional coordinates) of two points. Each arc segment 502 may bedefined by the coordinates of a starting point, an ending point, acenter point and a radius. Further, each arc segment 502 may have adirection of travel or rotation. The first representation supports aradius modification technique in a convenient and readily accessiblemanner. For each arc segment, the perpendicular offset between adjacentcontour rows is generally calculated such that no gap will be leftbetween corresponding arcs of adjacent rows. The sequence of linearsegments 500 and arc segments 502 must be contiguous and the radius ofthe arc segments 502 must be greater or equal to the minimum turningradius of the vehicle.

FIG. 15B depicts a second representation of the contour row or referencerow by a sequence of corners (504, 510, 516, and 524). Each corner maybe defined by one or more corner points (e.g., in two dimensional orthree dimensional coordinates). Each corner (504, 510, 516, and 524).may be defined by a vertex point and two outlying points spaced aparttherefrom. Accordingly, a first set of three associated corner points(A, B, and C) forms a first corner 504; a second set of corner points(B, C, and D) forms a second corner 510; a third set of corner points(C, D and E) forms a third corner 516; and a fourth set of corner points(D, E and F) forms a fourth corner 524.

The sequence of corners (504, 510, 516 and 524) are generallycontiguous. Each corner may be used to describe or represent theequivalent of a single arc in the first representation, for example.Corners may contain additional properties including an inside flag(indicative of an inside corner) or outside flag (indicative of anoutside corner), the radius of the arc, and the difference in radiibetween a corner (of a previous row) and a next corner (of a next row).For an outside corner, the convex side of the corner faces generallyoutward toward an edge of the work area.

A series of steps are required to generate the next adjacent row inaccordance with a translation technique. Under one translationtechnique, first the translator 34 or path planner 10 converts theprovided reference row in accordance with a first representation (e.g.,linear segments and arc segments) to its equivalent representation as asecond representation (e.g., corners). For example, one or more arcs areconverted to equivalent or corresponding corners. Second, the translator34 or path planner 10 translates the second representation into acontour path plan for at least a portion of the work area.

FIG. 15C is a third representation of a contour row in accordance with atransition sequence. FIG. 15C shows transitions. A transition is arepresentation of an instantaneous moment on the path and its principalattributes including its location (as a point) and its direction (as aunit vector). The transition may be defined in polar coordinates. Otherproperties include the radius of the associated arc and the rotationdirection at the location. As illustrated in FIG. 15C, a firsttransition has a first transition location 540 and a first transitiondirection 548 or heading; a second transition has a second transitionlocation 542 and a second transition direction 550 or heading, a thirdtransition has a third transition location 544 and a third transitiondirection 552 or heading; and a fourth transition has a fourthtransition location 554 and a fourth transition direction or heading.The transition locations may be defined by two or three dimensionalcoordinates, whereas the transition direction may be defined as angles.

FIG. 16 is an example of generation of a next contour row 602 associatedwith a previous arc segment 603 and a previous linear segment 605 of aprevious contour row 600. Here in the example of FIG. 16, the linearsegments (e.g., 605, 607) for adjacent rows may be determined bytranslation in the amount of perpendicular offset (d). The perpendicularoffset (d) is the required perpendicular offset distance needed so thatno gap is left between the two adjacent contour rows. The distance d maybe based upon the task width of the vehicle as previously described.However, where multiple vehicles are present and multi-vehicle collisionavoidance is required, the distance d may also consider greater the taskwidth and the body of wheel-base width. Further, the perpendicularoffset may be altered by an offset overlap allowance to allow adjacenttask widths to overlap slightly where a harvesting or cutting ofvegetation or crop is performed, or where an iterative repair process isapplied on a local basis within the work area.

For the arc segment 603, a simple contour translation will apply to formthe next arc segment 609 only under certain conditions (e.g., where w=pas described in FIG. 17). For the general case, a radius modification isrequired such that if the previous row 600 is the upper or outer row,the next row 602 has a radius reduction (c) in accordance with theradius modification technique. The radius reduction supportsminimization of overlap between one or more curved components (e.g., 603and 604) of the contour path plan, consistent with the translation ofany adjoining linear segment (e.g., 605, 607) associated with the curvedcomponent (e.g., 603).

In one illustrative embodiment, the radius modification is determined inaccordance with the following equations:${R_{i + I} = {R_{i} - p}};{p = \frac{d - {c*{\cos\left( {\Phi/2} \right)}}}{\cos\left( {\Phi/2} \right)}};$and c=|p−w|; and p≦w; where R_(i−1) is the new radius of curvedcomponent of the next row, R_(i) is the previous radius of curvedcomponent (e.g., previous arc segment (603)) of the previous row, p isthe radial spacing parameter between rows or the change in radiusbetween R_(i) and R_(i−1), c is the radius modification distance, whichmeans the displacement between a center point associated with a previouscurved component (e.g., previous arc segment having radius R_(i) and anext curved component (e.g., next arc segment) R_(i−1), d is therequired perpendicular offset distance needed between the translatedlinear components (e.g., so that no gap is left between the previous arcsegment and the next arc segment or between adjacent linear components).Φis the angle of the previous curved component for the previous row, andw is the vehicular width or the task width. The angle of the next arcsegment 604 may be based on the difference in radii between the previousarc segment 603 and the next arc segment 504. In one embodiment, theradial spacing parameter (p) is determined by a search process describedlater (e.g., A* search algorithm). If the radial spacing parameter isequal to vehicular width w, then a nesting contour solution is obtainedas set forth in FIG. 17 (and the perpendicular offset or row spacing (d)is approximately equal to the vehicular width (w)). However, a nestingcontour solution may be locally optimal for part of a contour path, butglobaly unsolvable or deficient for the complete contour path plan. Byusing the radial spacing parameter (p), consistent with the aboveequation the system and method can explore other solutions, andtherefore find a globally satisfying solution.

The next row 602 of FIG. 16 may be formed from a previous row 600 byapplying the third representation of FIG. 15C, for example. Once thevalue of the radial spacing parameter (p) (e.g., which may be set equalto the perpendicular offset distance (d) under certain circumstances),the next row can be produced by a translation technique, a radiusmodification technique or both with respect to the previous row (e.g., areference row). First, the minimum value of the radial spacing parameter(p) (e.g., again p may be set equal to d, where appropriate) for all thecurved components (e.g., corners) in a single row is calculated tosupport generally parallel rows that track each other. Alternately, eachindividual value of the radial spacing parameter (p) is used for eachcorresponding curved component. Second, a transition point is calculatedfor each curved component (e.g., corner) that will lie along the bisectline of FIG. 16 and along the next row. The vector of each transitionpoint will be perpendicular to its corresponding corner's bisect-line.The radius of the transition will be R_(i+1). Third, the path plannerdetermines a new or next contour row by connecting together thetransition points. For example, the path planner may use the “arc-paths”method that takes multiple transition points and produces a smooth pathconsisting of a curved component (e.g., an arc segment), a substantiallylinear component (e.g., a linear segment), and another curved component.The parameters for the arcs will be taken from the transition points(radius, vector, rotation-direction). The result will be a new contourrow that satisfies the constraints.

FIG. 17 is an example of a contour translation of new arc segment 503associated with the generation of a next contour row 502 associated witha previous arc of segment 501 of a previous contour row 500. FIG. 17represents a simple approach to computing the contour rows based ondirect geometric manipulation of the original reference row (e.g., orprevious contour row 500). For example, the approach of FIG. 17 may bebased on a direct translation. In this translation technique, the nextcontour row (e.g., next contour row 502) is computed by applying aperpendicular translation of magnitude w to the current row 500. Forexample, a new generally linear segment 507 is translated or spacedparallel to the original or previous linear segment 505 of a contour rowby a perpendicular offset distance (d) approximately equal to thevehicular width (w). This translation technique clearly works when therows are straight lines. However, when curved components (e.g., arcsegments) are involved it is not obvious the appropriate vector ormagnitude of translation required to ensure that no area is leftuncovered and that the overlap between the rows is minimized, unlessparticular geometry constraints are satisfied (e.g., where p issubstantially equal to w such that a nesting solution applies, such asset forth in FIG. 17). The approach of FIG. 17 produces workable, butinefficient, solutions with a limited set of simple reference rows.However, it is unable to effectively produce a contour coverage pathsuch as that in FIG. 14 without incurring excessive overlapping ofadjacent rows.

A radial spacing parameter (p) between the previous arc segment and thenext arc segment may be defined as approximately equal to the vehicularwidth (w). However, the perpendicular offset between the rows,designated d, may be calculated as a function of w. In general, d may bedetermined in accordance with the following equation: d=(p+c) * cos (Φ2)and; d≦w, where d is the required perpendicular offset distance (e.g.,selected so that no gap is left between the previous arc segment and thenext arc segment), Φ is the angle of the previous arc segment for theprevious row. Where, the radial spacing parameter (p) equals thevehicular width (w), the above equation may be simplified to thefollowing equation: d=w * cos (Φ/2).

FIG. 18 is an example of nesting contour associated with the generationof multiple next contour rows associated with an arc of a previouscontour row. FIG. 18 represents an iterative application of the processapplied in FIG. 17. FIG. 18 represents a simple geometric approach thatis well suited to simple arc paths and uses nesting (e.g., translation)rather than radius modification. In this approach, the outer adjacentrow to an inside arc (not shown) has its radius increased by thevehicular width (w) (or p=w) while using the same center point 809.Conversely, the inner adjacent row 802 to an outside arc 806 has itsradius decreased by vehicular width (w) while using the same centerpoint 809. This method can produce contour path plans that minimize thenumber of rows needed with no overlap or missed areas. However, itsapplicability is generally limited to simple cases of contour pathplans. Unsolvable problems occur when the radius of outside arcs isreduced to the minimum drivable radius or when adjoining arcs interferewith each other as the radii are changed as in FIG. 19 or between anoutside and inside arc as in FIG. 20.

Because of the significant restrictions of the simple translation ornesting approach of FIG. 18, the region-filling module 12 or pathplanner 10 uses a hybrid approach that combines the advantages oftranslation and nesting, while overcoming their limitations.

FIG. 19 is an illustrative example of the resolution of a firstoutside-curved component 900 interfering with a second outside curvedcomponent 902 (e.g., interference between two outside-corners). Anoutside curved component (e.g., 900 or 902) has its convex side facingthe outer boundary of the region or work area. In FIG. 19, an innercontour row 919 (e.g., here, the lower contour row) is determined basedon an outer contour row 909 (e.g., here, the upper contour row) thatincludes a first curved component 900 (e.g., a first corner) and asecond curved component 902 (e.g., a second corner) with the potentialpresence of an intervening generally linear component. The generallylinear component may be located where the outer path contour 909intersects with the bisect line 920. The path planner 10 replaces thefirst curved component 900 and the second curved component 902 in theprevious row 909 with a single new curved component 904 for in the nextcontour row 919 or inner contour row. A critical point 910 of the singlecurved component 904 is estimated based on the critical points (906,908) of the first curved component 900 and the second curved component902 with respect to a first bisect line 914 and a second bisect line918. A procedure for resolving the interference of between the outsidecurved components (900 and 902) of FIG. 19 is discussed earlier inconjunction with the description of FIG. 4.

FIG. 20 is an illustrative example of the resolution of an interferencebetween an outside curved component 990 and an inside curved component991. For example, FIG. 20 is an illustrative example of the resolutionof outside corner-inside corner interference (illustrated by theinterference region or hatched region 993). A potential nonconformity orpath formation prohibition is identified if (1) proposed arc centerseparation distance 954 between two curved components (995, 997) on aproposed contour are so close that the two curved components (995, 997)touch or approach each other in a manner that is less than a minimumrequisite clearance (e.g., interference of overlap in the hatched region993); and (2) the curved components (995, 997) are opposite curvedcomponents. Proposed arc center separation distance 954 means that thedistance between centerpoints 960 and 962 of the curved components. Aprevious arc center separation distance 999 means that the distancesbetween centerpoints 956 and 958 of the curved components. A minimumrequisite clearance may mean that the proposed arc separation distances999 is greater than or equal to the previous arc separation distance999.

Opposite curved components means that one curved component is curved inan opposite manner to the other curved component. For example, anoutside curved component 995 is curved oppositely with respect to aninside curved component 997. The path planner 10 resolves theinterference or conflict between the opposite curved components (asillustrated in FIG. 20) by avoiding the production of a tracking contourwith opposite curved components. The opposite curved components mayinteract to cause the tracking contour to overlap or the vehicle to makean unwanted loop.

In another embodiment the path planner 10 solves the interferenceproblem of FIG. 20 changing the parameters of the reference row oradjacent row that is being tracked to establish a subsequent row. Instill another embodiment, the path planner 10 divides the work area intotwo distinct coverage paths (e.g., contour coverage paths) to cover afirst region and a second region. The first region covers one curvedcomponent and the second region is configured to cover an oppositecomponent.

FIG. 21A illustrates a work area containing one or more obstacles 850 orno-entry areas 852 and having a defined reference contour row 970. Thereference contour row 970 may be specified in accordance with arepresentation, such as linear segments and curved segments that areinterconnected. The region filling module 12 or path planner 10 forms areference contour row. The reference contour row refers to a target linewhich the tracking contour rows track in FIG. 21B. For example, thereference contour row of FIG. 21A is consistent with the referencecontour row of step S100 of FIG. 3A.

FIG. 21B illustrates the defining of transparency 972 of contours thattrack the reference contour row on a first side 969 of the referencecontour row and a second side 971 of the reference contour row. Thereference contour 970 is tracked to create a transparency 972 that isoverlaid on the work area. The routine of the region-filling module 12will use this transparency to create the graph or candidate path plansthat may be searched for a preferential contour path plan. Thetransparency 972 overlaps a boundary of the work area and represents anintermediate step in the formation of a contour path plan. For example,the reference contour row of FIG. 21B is consistent with the step S314of FIG. 3A.

FIG. 21C illustrates a coverage solution that uses contour components tocover the work area of FIG. 21A. The contour rows are interconnectedwith loops in a preferential order to form a generally continuous pathplan of back-and-forth sweeps. The coverage solution of FIG. 21C isconsistent with steps S314 through S320 of FIG. 3A, for example. Thecoverage solution that is produced in FIG. 21C is based on the input ofthe reference row contour 970 of FIG. 21A. The coverage solution wascreated using the turn outside option so the turns are outside the workarea.

In any of the method or path planning systems disclosed herein, a datapath planner 10 may invoke a fail-safe mode. In one embodiment, thefail-safe mode is described as follows. To generate a back and forthcontour sweep use the region-filling routine or method of this inventionas described above with the desired contour line specified in the“reference contour” array of line segments. When an invalid target lineis passed, the fill area routine defaults to using a straight back andforth sweep pattern. The straight back and forth sweep will use theangle of the longest straight line in the object description as theorientation of the sweeps because this line is likely to produce longerrows and hence fewer end-of-row turns. The contour program code of thepath planner 10 tries to optimize the contour rows such that the overlapbetween rows is minimized. However, in most cases the next contour rowill need to overlap the previous row by some distance. Overlapping theprevious rows can affect the end-of-row turns by requiring a loop tocomplete some turns.

The path planner 110 of FIG. 22 is similar to the path planner 10 ofFIG. 1, except the path planner 110 further comprises a linear pathestimator 51, a contour path estimator 53, a turn estimator 55, and adata processor 57 for supporting the determination of whether to use alinear path plan or a contour path plan to service a defined work area.The linear path estimator 51 estimates a linear length (or linear timeduration) for covering a work area with a linear coverage path. Incontrast, the contour path estimator 53 estimates a contour length (orcontour time duration) for covering a work area with a contour coveragepath. The turn estimator 55 estimates the length (or duration) of turnsfor end rows to cover the work area for the linear coverage path and thecontour coverage path. The data processor 57 adds the length of turnsfor the linear coverage pattern to the linear length to obtain a firsttotal length and the length of turns for the contour coverage pattern tothe contour length to obtain the second total length. The data processor57 determines the shorter of the first total length or the second totallength to assign a corresponding preferential path plan as the linearpath plan or the contour path plan.

In an alternate embodiment, the data processor 57 determines the lesserof the first total time associated with the linear coverage path and thesecond total time associated with the contour coverage path, where firsttotal time comprises the linear time duration plus the appropriate turntime duration and the second total time comprises the contour timeduration plus the appropriate turn time duration. The data processor 57may apply or recommend (e.g., via the user interface 21) a contour pathplan, a linear path plan, or both to cover a particular work area. Thework area may be defined by the perimeter training module 14.

FIG. 23 is a method for determining whether to use a linear path plan ora contour path plan. The method of FIG. 23 begins with step S300.

In step S300, a linear path estimator 51 estimates a linear pathestimate of at least one of a total length (in distance), a totalelapsed time, and a total energy consumption for a vehicle to execute alinear coverage path and covers the region (e.g., work area). Forexample, the path estimator 51 estimates the total length or totalelapsed time for the vehicle to traverse the linear path segments thatcover the region (e.g., work area). For a linear coverage pattern, backand forth sweeps produce generally parallel straight lines that coversthe work area. The estimator considers vehicular constrains such asturning radius, maximum speed, energy consumption, and the like.

In step S302, the turn estimator 55 estimates a first turn estimate ofat least one of a total length, a total time, and a total energyconsumption associated with the turns at the end of rows of thegenerally linear path plan. For example, the turn estimator 55 estimatesthe elapsed time for the vehicle to complete all of the turns (e.g., endof row turns) that support the linear coverage path of step S300. Underone procedure for carrying out step S302, a turn estimator estimates thenumber of turns (e.g., end row turns) required to support the linearcoverage path plan and then converts the number of turns into a totalturn length, a total turn time, and a total turn energy consumption.

In step S304, a data processor 57 determines a first figure of merit fora corresponding linear coverage path that covers the work area. Thefirst figure of merit may be determined by adding the linear estimate tothe corresponding first turn estimate. In one example, the first figureof merit comprises a total estimated energy consumption for a particularvehicle to complete a corresponding particular linear coverage path,which includes traversing the linear segments of step S300 and the turnsof step S302. In another example, the first figure of merit comprises atotal estimated time duration for a particular vehicle to complete acorresponding particular linear coverage path, which includes traversingthe linear segments of step S300 and the turns of step S302. In anotherexample, the first figure of merit comprises a total estimated lengthfor a particular vehicle to complete a corresponding particular linearcoverage path, which includes traversing the linear segments of stepS300 and the turns of step S302.

In step S306, a contour path estimator 53 estimates a contour pathestimate of at least one of a total length (in distance), a totalelapsed time, and a total energy consumption for a vehicle to execute acontour coverage path for a region. For example, the contour pathestimator 53 estimates the total length or total elapsed time for thevehicle to traverse the contour path segments that cover the region. Fora curved coverage region, contour sweeps cover a region with adjacentcurved paths. Such paths resemble the patterns of contour lines found ona map of a hill slope. The estimator 53 considers vehicular constrainssuch as turning radius, maximum speed, energy consumption, and the like.

In step S308, the turn estimator 55 estimates a second turn estimate ofat least one of length, time duration and energy consumption associatedwith the requisite number of turns for ends of rows for the estimatedcontour path of step S306. For example, the turn estimator 55 estimatesthe elapsed time for the vehicle to complete the turns that support thecontour coverage path of step S306. Under one procedure for carrying outstep S308, a turn estimator estimates the number of turns (e.g., end rowturns) required to support the contour coverage path plan and thenconverts the number of turns into a total turn length, a total turntime, and a total turn energy consumption.

In step S310, a data processor 57 determines a second figure of meritfor a corresponding contour coverage path. The second figure of meritmay be determined by adding the contour path estimate to thecorresponding second turn estimate. In one example, the second figure ofmerit comprises a total estimated energy consumption for a particularvehicle to complete a corresponding particular contour coverage path,which includes traversing the contour segments of step S306 and theturns of step S308. In another example, the second figure of meritcomprises a total estimated time duration for a particular vehicle tocomplete a corresponding particular contour coverage path, whichincludes traversing the linear segments of step S306 and the turns ofstep S308. In yet another example, the second figure of merit comprisesa total estimated energy consumption of the vehicle to complete acorresponding particular contour coverage path, which includestraversing the linear segments of step S306 and the turns of step S308.

In step S312, the data processor 57 determines whether to select thelinear path or the contour coverage path based on the determined firstfigure of merit in step S304 and the second figure of merit of stepS310. If the second figure of merit is superior to the first figure ofmerit, then the data processor 57 may select the contour coverage pathas the preferential coverage path. For example, the data processor 57may select a preferential path with the shortest length, shortest timeor the lowest energy consumption based on the determined first figure ofmerit in step S304 and second figure of merit of step S310. Thepreferential path may be the contour path plan, but need not be.

Under certain circumstances, the contour coverage path for area coveragehas efficiency or energy consumption advantages over simple parallelstraight lines or a linear coverage path. For example, when the contoursrun adjacent to a long side of the region to be covered, the contourcoverage pattern tends to minimize the number of required end-of-rowturns, which reduces the time needed to complete the operation.Additionally, by maximizing the length of the rows, missed areas areminimized and overlapping between rows can be minimized. The firstfigure of merit and the second figure of merit are intended to capturethe efficiency or energy consumption advantages noted above and tosupport analysis thereof.

Although it is preferable that the reference contour is chosen such thatthe energy consumption for completion of the resultant coverage pathwill be minimized in accordance with the method of FIG. 23 or anothertechnique, the user may select a contour reference path for otherreasons independent of FIG. 23 or any comparison to corresponding linearpaths for a region.

The method and path planning system may be used for filling a regionwith contour rows. It is capable of utilizing an initial reference rowto produce high quality contour rows that cover a given region. Themethod and system is robust and produces solutions quickly, whileminimizing overlap between adjacent rows and providing resolution ofpotential nonconformities and path formation rule violations.

Having described the preferred embodiment, it will become apparent thatvarious modifications can be made without departing from the scope ofthe invention as defined in the accompanying claims.

1. A method for planning a path of a vehicle, the method comprising: defining a reference row having a reference contour in a work area; establishing a representation of the defined reference row, the reference row comprising at least one of a generally curved component and a generally linear component, wherein the representation comprises one or more critical points of material directional change of the vehicle, each critical point defined by a pair of location data and a corresponding heading, each pair assigned a sequence for traversing the critical points; and generating one or more contour rows with a tracking contour that tracks or mirrors the reference contour based on a vehicular width and a radius difference parameter associated with the curved component.
 2. The method according to claim 1 wherein the representation of the curved component comprises an arc segment and wherein the linear component comprises a linear segment.
 3. The method according to claim 2 wherein the establishing of the representation comprises defining the arc segment as a center point, a start point, an end point and a radius, where the arc segment has a radius greater than the minimum turning radius of the vehicle; wherein the establishing of the representation comprises defining the linear segment as two points.
 4. The method according to claim 1 wherein the representation comprises one or more corners defined by location data and a sequence for traversing the corners.
 5. The method according to claim 1 wherein the representation comprises one or more critical points of material directional change of the vehicle, each critical point defined by a pair of location data and a corresponding heading, each pair assigned a sequence for traversing the critical points.
 6. The method according to claim 1 wherein the defining further comprises defining the reference row having a reference contour that follows along a boundary contour of a boundary of the work area.
 7. The method according to claim 1 wherein if the radius difference parameter generally equals the vehicular width, a nesting solution applies to adjacent rows on a local basis.
 8. The method according to claim 1 further comprising: identifying the presence of two adjacent outside arcs separated by a linear segment in an outer contour row located toward an outer boundary of the work area; and determining a single outside arc for an inner contour row that tracks the outer contour row, the inner contour row located closer to an interior of the work area than the outer contour row.
 9. The method according to claim 1 further comprising: identifying a presence of an inside arc and outside arc being adjacent to each other, in a proposed contour row where such inside arc and outside arc would cross over each other; and applying an iterative repair process to reformulate the proposed contour row.
 10. The method according to claim 1 wherein the generating comprises applying a search algorithm to possible candidate values of the radius difference parameter, wherein the search space is limited such that the radius difference parameter is bounded by a candidate radius difference parameter generally equal to or less than the vehicular width.
 11. The method according to claim 1 wherein generating comprises applying a search algorithm to possible candidate values of the radius difference parameter, wherein the search space is limited such that search is started with the radius difference parameter equal to the vehicular width and the radius difference parameter is decreased therefrom.
 12. The method according to claim 1 further comprising: determining a first figure of merit for a corresponding linear coverage path for covering a work area, the first figure of merit indicating at least one of a total energy consumption, a total distance, or a total time duration of the vehicle for completing the linear coverage path; determining a second figure of merit for a corresponding contour coverage path for covering the work area, at least one of a total energy consumption, a total distance, or a total time duration of the vehicle for completing the contour coverage path; selecting the contour coverage path if the second figure of merit is superior to the first figure of merit.
 13. The method according to claim 12 wherein the determining of the first figure of merit further comprises: estimating a total length in distance for the vehicle to execute a linear coverage path for the work area; and estimating the number or corresponding length of turns at the end of rows for the linear coverage path.
 14. The method according to claim 13 wherein the determining of the second figure of merit further comprises: estimating a total length in distance for the vehicle to execute a contour coverage path for the work area; and estimating the number or corresponding length of turns at the end of rows for the contour coverage path.
 15. A path planner for planning a path of a vehicle, the path planner comprising: a definer for defining a reference row having a reference contour in a work area; a representation former for establishing a representation of the defined reference row. The representation comprising an arc segment and at lest one of a linear segment and a transition; and a generator for generating one or more contour rows with a tracking contour that tracks or mirrors the reference contour based on a vehicular width and a radius difference parameter associated with the arc segment; the contour rows generated by at least one of a translation technique, a radius modification technique, and a hybrid technique; where the generator comprises a radius modifier for selecting the radius difference parameter such that if the radius difference parameter generally equals the vehicular width, a nesting solution applies to adjacent rows on a local basis.
 16. The path planner according to claim 15 wherein the definer defines the reference row having a reference contour that follows along a boundary contour of a boundary of the work area.
 17. The path planner according to claim 16 wherein the reference row is contiguous with the boundary.
 18. The path planner according to claim 15 wherein the definer defines a reference row that does not track a boundary of the work area.
 19. The path planner according to claim 15 wherein the representation former defines the arc segment as a center point, a start point, an end point and a radius, where any arc segment has a radius greater than the minimum turning radius of the vehicle.
 20. The path planner according to claim 15 wherein the representation former defines the linear segment as two points.
 21. (canceled)
 22. The path planner according to claim 15 further comprising: an interference module for identifying the presence of two adjacent outside arcs separated by a linear segment in an outer contour row located toward an outer boundary of the work area; and the interference module determining a single outside arc for an inner contour row that tracks the outer contour row, the inner contour row located closer to an interior of the work area than the outer contour row.
 23. The path planner according to claim 15 further comprising: an interference module for identifying a presence of an inside arc and outside arc being adjacent to each other, in a contour row where such inside arc and outside arc would cross over each other; and the interference module applying an iterative repair process to reformulate the contour row.
 24. (canceled)
 25. The path planner according to claim 15 wherein generator further comprises a search engine for applying a search algorithm to possible candidate values of the radius difference parameter, wherein the search space is limited such that search is started with the radius difference parameter equal to the vehicular width and the radius difference parameter is decreased therefrom.
 26. The path planner according to claim 15 further comprising: a linear path estimator for estimating a linear path estimate of at least one of a total length, a total time, and a total energy consumption for a vehicle to execute a generally linear path plan; a contour path estimator for estimating a contour path estimate of at least one of a total length, a total time, and a total energy consumption for a vehicle to execute a generally contour path plan; a turn estimator for estimating turn estimates of at least one of a length, time duration and energy consumption associated with the turns at end of rows of the generally linear path plan and the contour path plan; a data processor for determining a first figure of merit for the corresponding linear path and for determining a second figure of merit for the corresponding contour path plan based on the linear path estimate, the contour path estimate, and the turn estimates; the data processor adapted to select the contour coverage path if the second figure of merit is superior to the first figure of merit. 